This is a note to let you know that I've just added the patch titled
jbd2: fix race between jbd2_journal_remove_checkpoint and ->j_commit_callback
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
jbd2-fix-race-between-jbd2_journal_remove_checkpoint-and-j_commit_callback.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 794446c6946513c684d448205fbd76fa35f38b72 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Date: Wed, 3 Apr 2013 22:06:52 -0400
Subject: jbd2: fix race between jbd2_journal_remove_checkpoint and ->j_commit_callback
From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
commit 794446c6946513c684d448205fbd76fa35f38b72 upstream.
The following race is possible:
[kjournald2] other_task
jbd2_journal_commit_transaction()
j_state = T_FINISHED;
spin_unlock(&journal->j_list_lock);
->jbd2_journal_remove_checkpoint()
->jbd2_journal_free_transaction();
->kmem_cache_free(transaction)
->j_commit_callback(journal, transaction);
-> USE_AFTER_FREE
WARNING: at lib/list_debug.c:62 __list_del_entry+0x1c0/0x250()
Hardware name:
list_del corruption. prev->next should be ffff88019a4ec198, but was 6b6b6b6b6b6b6b6b
Modules linked in: cpufreq_ondemand acpi_cpufreq freq_table mperf coretemp kvm_intel kvm crc32c_intel ghash_clmulni_intel microcode sg xhci_hcd button sd_mod crc_t10dif aesni_intel ablk_helper cryptd lrw aes_x86_64 xts gf128mul ahci libahci pata_acpi ata_generic dm_mirror dm_region_hash dm_log dm_mod
Pid: 16400, comm: jbd2/dm-1-8 Tainted: G W 3.8.0-rc3+ #107
Call Trace:
[<ffffffff8106fb0d>] warn_slowpath_common+0xad/0xf0
[<ffffffff8106fc06>] warn_slowpath_fmt+0x46/0x50
[<ffffffff813637e9>] ? ext4_journal_commit_callback+0x99/0xc0
[<ffffffff8148cae0>] __list_del_entry+0x1c0/0x250
[<ffffffff813637bf>] ext4_journal_commit_callback+0x6f/0xc0
[<ffffffff813ca336>] jbd2_journal_commit_transaction+0x23a6/0x2570
[<ffffffff8108aa42>] ? try_to_del_timer_sync+0x82/0xa0
[<ffffffff8108b491>] ? del_timer_sync+0x91/0x1e0
[<ffffffff813d3ecf>] kjournald2+0x19f/0x6a0
[<ffffffff810ad630>] ? wake_up_bit+0x40/0x40
[<ffffffff813d3d30>] ? bit_spin_lock+0x80/0x80
[<ffffffff810ac6be>] kthread+0x10e/0x120
[<ffffffff810ac5b0>] ? __init_kthread_worker+0x70/0x70
[<ffffffff818ff6ac>] ret_from_fork+0x7c/0xb0
[<ffffffff810ac5b0>] ? __init_kthread_worker+0x70/0x70
In order to demonstrace this issue one should mount ext4 with mount -o
discard option on SSD disk. This makes callback longer and race
window becomes wider.
In order to fix this we should mark transaction as finished only after
callbacks have completed
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/jbd2/commit.c | 50 ++++++++++++++++++++++++++++----------------------
include/linux/jbd2.h | 1 +
2 files changed, 29 insertions(+), 22 deletions(-)
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -325,7 +325,7 @@ void jbd2_journal_commit_transaction(jou
int space_left = 0;
int first_tag = 0;
int tag_flag;
- int i, to_free = 0;
+ int i;
int tag_bytes = journal_tag_bytes(journal);
struct buffer_head *cbh = NULL; /* For transactional checksums */
__u32 crc32_sum = ~0;
@@ -1044,7 +1044,7 @@ restart_loop:
journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
spin_unlock(&journal->j_history_lock);
- commit_transaction->t_state = T_FINISHED;
+ commit_transaction->t_state = T_COMMIT_CALLBACK;
J_ASSERT(commit_transaction == journal->j_committing_transaction);
journal->j_commit_sequence = commit_transaction->t_tid;
journal->j_committing_transaction = NULL;
@@ -1059,38 +1059,44 @@ restart_loop:
journal->j_average_commit_time*3) / 4;
else
journal->j_average_commit_time = commit_time;
+
write_unlock(&journal->j_state_lock);
- if (commit_transaction->t_checkpoint_list == NULL &&
- commit_transaction->t_checkpoint_io_list == NULL) {
- __jbd2_journal_drop_transaction(journal, commit_transaction);
- to_free = 1;
+ if (journal->j_checkpoint_transactions == NULL) {
+ journal->j_checkpoint_transactions = commit_transaction;
+ commit_transaction->t_cpnext = commit_transaction;
+ commit_transaction->t_cpprev = commit_transaction;
} else {
- if (journal->j_checkpoint_transactions == NULL) {
- journal->j_checkpoint_transactions = commit_transaction;
- commit_transaction->t_cpnext = commit_transaction;
- commit_transaction->t_cpprev = commit_transaction;
- } else {
- commit_transaction->t_cpnext =
- journal->j_checkpoint_transactions;
- commit_transaction->t_cpprev =
- commit_transaction->t_cpnext->t_cpprev;
- commit_transaction->t_cpnext->t_cpprev =
- commit_transaction;
- commit_transaction->t_cpprev->t_cpnext =
+ commit_transaction->t_cpnext =
+ journal->j_checkpoint_transactions;
+ commit_transaction->t_cpprev =
+ commit_transaction->t_cpnext->t_cpprev;
+ commit_transaction->t_cpnext->t_cpprev =
+ commit_transaction;
+ commit_transaction->t_cpprev->t_cpnext =
commit_transaction;
- }
}
spin_unlock(&journal->j_list_lock);
-
+ /* Drop all spin_locks because commit_callback may be block.
+ * __journal_remove_checkpoint() can not destroy transaction
+ * under us because it is not marked as T_FINISHED yet */
if (journal->j_commit_callback)
journal->j_commit_callback(journal, commit_transaction);
trace_jbd2_end_commit(journal, commit_transaction);
jbd_debug(1, "JBD2: commit %d complete, head %d\n",
journal->j_commit_sequence, journal->j_tail_sequence);
- if (to_free)
- jbd2_journal_free_transaction(commit_transaction);
+ write_lock(&journal->j_state_lock);
+ spin_lock(&journal->j_list_lock);
+ commit_transaction->t_state = T_FINISHED;
+ /* Recheck checkpoint lists after j_list_lock was dropped */
+ if (commit_transaction->t_checkpoint_list == NULL &&
+ commit_transaction->t_checkpoint_io_list == NULL) {
+ __jbd2_journal_drop_transaction(journal, commit_transaction);
+ jbd2_journal_free_transaction(commit_transaction);
+ }
+ spin_unlock(&journal->j_list_lock);
+ write_unlock(&journal->j_state_lock);
wake_up(&journal->j_wait_done_commit);
}
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -470,6 +470,7 @@ struct transaction_s
T_COMMIT,
T_COMMIT_DFLUSH,
T_COMMIT_JFLUSH,
+ T_COMMIT_CALLBACK,
T_FINISHED
} t_state;
Patches currently in stable-queue which might be from dmonakhov@xxxxxxxxxx are
queue-3.4/ext4-fix-journal-callback-list-traversal.patch
queue-3.4/jbd2-fix-race-between-jbd2_journal_remove_checkpoint-and-j_commit_callback.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html